The conventional knock-out type automatic pencil usually has its inner tube which contains the pencil lead, its clamp which holds the lead and its head which serves as guide and protection to the lead made into individual parts. Fabrication of these parts and assembling thereof are quite complicated, thus resulting in high manufacturing cost. In addition, the head part and the clamp of inner tube are assembled with respective male-female threads formed at a fixing collar and the front end of the outer barrel. The improper assembling and the movement during writing would cause the threading to loose thereby changes the length of threading between the head with inner tube and the fixing collar, or between the fixing collar and the outer barrel. It is therefore difficult to assure the proper advancing of the lead, too short or too long of the extrusion of lead makes the lead easily to be broken. Besides, the said parts are usually made of metal such as copper, the cost of which is comparatively higher. The manufacturing of a claw-type clamp which splits at the front end, requires machinery of high precision, which in turn calls for a higher investment in manufacturing equipment.
In view of the abovesaid drawbacks, the present inventor has developed a novel knock-out type automatic pencil with improved structure, namely, to have the inner tube, clamp and the head made into an integrate assembly with plastic material.